Hybrid magnetically suspended and rotated centrifugal pumping apparatus and method

ABSTRACT

An apparatus and method for a centrifugal fluid pump for pumping sensitive biological fluids, which includes (i) an integral impeller and rotor which is entirely supported by an integral combination of permanent magnets and electromagnetic bearings and rotated by an integral motor, (ii) a pump housing and arcuate passages for fluid flow and containment, (iii) a brushless driving motor embedded and integral with the pump housing, (iv) a power supply, and (v) specific electronic sensing of impeller position, velocity or acceleration using a self-sensing method and physiological control algorithm for motor speed and pump performance based upon input from the electromagnetic bearing currents and motor back emf—all fitly joined together to provide efficient, durable and low maintenance pump operation. A specially designed impeller and pump housing provide the mechanism for transport and delivery of fluid through the pump to a pump output port with reduced fluid turbulence.

RELATED APPLICATIONS

This application is a continuation application of pending U.S. patentapplication Ser. No. 09/602,471, filed Jun. 23, 2000, entitled “PumpHaving a Magnetically Suspended Rotor With One Active Control Axis,” nowU.S. Pat. No. 6,394,769, which claims priority and is a continuationfrom pending PCT Patent Application No. PCT/US99/08870, filed Apr. 22,1999, entitled “Implantable Centrifugal Blood Pump With Hybrid MagneticBearings,” which claims priority and is a continuation from abandonedU.S. patent application Ser. No. 09/064,352, filed Apr. 22, 1998,entitled “Implantable Centrifugal Blood Pump With Hybrid MagneticBearings,” which was a continuation-in-part of U.S. patent applicationSer. No. 08/850,598, filed May 2, 1997, entitled “Hybrid MagneticallySuspended and Rotated Centrifugal Pumping Apparatus and Method,” nowU.S. Pat. No. 6,074,180, which claims priority from U.S. ProvisionalPatent Application No. 60/016,856, filed May 3, 1996, entitled “HybridMagnetically Suspended and Rotated Centrifugal Pumping Apparatus andMethod.”

BACKGROUND OF THE INVENTION

1. The Field of the Invention

This invention relates to magnetically supported and rotated rotors and,more particularly, to a centrifugal pumping apparatus and method whosedisk-like impeller is magnetically suspended and rotated in acontact-free manner, the rotation speed of the impeller being controlledand changed electronically by fluid pressure and impeller positioningalgorithms.

2. The Relevant Technology

Historically, fluid pumps are of many and varied types andconfigurations, all performing essentially the same end result, namely,to provide fluid movement from one point to another. All pumps have asimilar characteristic in that fluid is drawn into the pump through avessel or pipe by a vacuum created by pump operation. In addition to theprimary force of vacuum, secondary forces such as gravity, impellerinertia, or existing pipe/vessel fluid pressures also have an effect onfluid flow. Operation of the pumping mechanism creates a fluid pressureand/or fluid velocity which subsequently creates the vacuum that drawsfluid into the pump through a pump inlet port. Fluid from the inlet portis transported throughout the pump by the pump mechanism whichsubsequently directs fluid to a pump outlet port.

Fluid pump configurations vary mostly by adaptation to function. Forexample, lift and force pumps utilize a reciprocating motion to displacefluid, whereas vacuum pumps create a vacuum that is used to displacefluid. Rotating axial-flow pumps utilize propeller-like blades attachedto a rotating shaft to accomplish the displacement of fluid. Jet pumpsutilize a steam-jet ejector which enters a narrow chamber inside thepump and crates a low-pressure area that correspondingly creates asuction that draws the fluid into the chamber from an inlet port.Although, other pump types could be specified, more specific referencewill be made hereafter to fluid pumps for a sensitive fluid such asblood which are more easily adaptable to environments where size andgeometry of the pump are critical.

The rotating centrifugal pump is, by nature, more tightly configured andreadily adaptable to pumping of sensitive fluids. Blood flow pumps haverelatively low flow rate performance characteristics compared to manyordinary industrial applications yet have significant pressure riserequirements. Centrifugal pumps are well suited to such applicationsrather than axial flow pumps or other designs. This leads to the use ofa centrifugal pump design for the preferred embodiment of thisinvention. The pump includes several ribs or vanes mounted to animpeller whose rotational force impels fluid toward the outside of therotor by centrifugal force. Centrifugal pumps traditionally possess ashaft-mounted impeller immersed in the fluid, where the shaft extendsthrough a seal and bearing apparatus to a drive mechanism. Revolvingvanes of the impeller create a partial vacuum near the center of theaxis of rotation which correspondingly draws in fluid through the intakeopening of the pump. A smooth pump volute is located in the pumpstationary component to assure the smooth flow of pumped fluid from theexit of the impeller to the pump exit passage. The volute accumulatesthe pump flow as it exits the pump impeller and performs the function ofincreasing the fluid pressure (head) by converting fluid kinetic energy(velocity) to potential energy (pressure or head). Although centrifugalpumps do not require valves for movement of fluid, pump geometry must besuch that fluid drawn in through the input opening will continue throughthe pump mechanism and on to the outlet port without significantinternal fluid leakage or inefficiencies.

These prior art pumps are known to have problems. For example, it iswell documented that shaft seals as configured in conventionalcentrifugal pumps are notoriously susceptible to wear, failure, and evenattack by certain fluids, thus resulting in leakage problems. It is alsowell known that pumps for some fluids require more careful designconsideration and require specific pumping techniques in order to avoidfluid damage, contamination, and other undesirable conditions. Forexample, fluids such as corrosive fluids (acids or caustics) orsensitive fluids such as blood, require special consideration such thatseals do not leak and thereby lose integrity of the fluid. Pumping ofsensitive fluids, such as blood, by continuous flow pumps requireshighly reliable and non-damaging bearings to support the rotatingimpeller. Prior art pumps have very significant problems with bearingsneeded to support the impeller as it rotates. Ball and other rollingelement bearings can only be employed if isolated from the sensitivefluid (blood) by shaft seals and lubricated with non-body fluids. Inthis situation, all of the sealing problems indicated above apply. Ifthe conventional ball or other rolling element hearings employ thesensitive fluid as a lubricant, the sensitive fluid living properties,such as red blood cells in blood, are destroyed in a short period oftime due to being ground between the rolling components in the bearings.Thrust and radial fluid film bearings, lubricated with the sensitivefluid, have been employed in some prior art pumps. These have beensubject to poor performance and/or many failures due to seizure of therotating component in the stationary component, production of thrombosis(clotting), damage to the sensitive fluid due to hemolysis (high shear),and other problems.

Fluid film bearings also do not provide any information on theinstantaneous pump pressures and flow rates that can be employed forspeed control of the motor to match physiological needs to future pumpperformance. Conventional ball bearings and fluid film thrust and radialbearings do not have the long term reliability required for pumps inwhich fluid stasis and high fluid shear stress must be avoided, such asblood pumps. Furthermore, ball bearings have a limited life whenemployed in the pumping of sensitive fluids and often must be lubricatedby an external lubricating fluid which requires seals to contain thelubricating fluid. Transport and containment of lubricating fluid forbearings increases the overall size of the pump housing as well asincreasing complexity of operation due to extra vessels and mechanismsused to deliver and cool lubricating fluid, thereby making pumpapparatus non-implantable infused to replace natural heart functions.Therefore, the relatively short life of fluid pumps with shafts andconventional bearings makes them unsuitable for implanting in bodycavities for the long term replacement of natural heart functions.

Furthermore, pumping of blood involves specific known hazards typicallyassociated with shaft seals for impeller-type blood pumps due to pocketsof fluid being susceptible to stagnation and excessive heat. Furtherstill, pumping sensitive fluids, such as blood, requires carefulconsideration of geometry of impeller vanes and pump housing. Excessivemechanical working and heating of blood causes blood components tobreakdown by hemolysis and protein denaturization, which leads to bloodcoagulation and thrombosis.

Avoidance of blood damaging effects of pump operation is bestaccomplished by natural heart function. The natural heart has two basicfunctions, each side performing a different pumping function. The rightside of the natural heart receives blood from the body and pumps it tothe lungs, whereas the left side of the natural heart collects bloodfrom the lungs and pumps it to the body. The beating of the naturalheart, in combination with heart valves, provides blood pumping actionin a pulsatile, remarkably smooth and flowing manner. Blood flow(cardiac output) of the natural heart is primarily regulated by venousreturn, otherwise known as pump preload. However, due to diseases oraccident, natural heart functions can be partially or totally lost.Mechanical apparatus developed to replace natural heart functionshistorically ranged in size from extremely large in the earliestheart-lung or pump oxygenator apparatus to more recent apparatus whosesize and function more closely resembles that of the natural heart.

In addition to total heart replacement, development of other mechanicalapparatus focuses on replacement of a portion of the function of thenatural heart, such as a ventricular assist device that aids a failingleft ventricle weakened by disease or other damage. A primaryconsideration for natural heart function replacement, whether partial ortotal, is that blood must be pumped throughout the entire apparatus in agentle, low thermal, and non-destructive manner. For example, if a pumpimpeller supported by mechanical bearings comes in contact with blood,relative movement between parts of the bearings results in excessivemechanical working of the blood which causes blood cells to rupture,resulting in hemolysis. Another mechanical effect that can injure bloodis formation of regions within the pump where blood is semi-stagnant orwhere blood will eddy without sufficient blood exchange, therebycreating the equivalent to blood stagnation. The result of bloodstagnation often is coagulation of the blood (thrombosis), whichcorrespondingly causes blood to cease to flow at all. Yet another effectthat can injure blood is excessive heating due to friction of a sidewallof the pump or other pumping mechanisms as blood passes through thepump. Specifically, side wall friction caused by abrupt angular changesof internal pump geometry requires blood to follow harsh changes ofdirection and thereby creates excessive mechanical working of bloodwhich causes blood cell rupture or activation of blood platelets andcorresponding hemolysis and thrombosis. Yet another effect that caninjure blood is caused by inefficient pump operation whereby a largepart of the energy supplied to the pump appears as heat discharged intothe blood which damages blood by overheating and coagulation. Notably,because blood albumen begins to denature at 42 degrees Centigrade,inefficiencies in pump operation which result in overheating of theblood will cause a very serious and life threatening condition.

The before mentioned conditions of stagnation, harsh pump geometry,turbulence and/or heating will activate blood platelets and/or damageoxygen-carrying red blood cells. Damage to blood starts a chain reactionthat forms a thrombus with potential to block blood vessels, starvingthe tissues it nourishes, and leading to a serious, life threateningcondition. Numerous attempts to avoid the foregoing problems associatedwith pumping blood have been made using flexible diaphragms andcollapsible tubing in roller pumps However, the continual flexing of thediaphragm and/or tubing material is known to change the blood-contactingproperties of the material resulting in material fatigue, dislodgedfragments of the internal wall of the flexible material, and embolipassed into the bloodstream by the fragments.

In addition to the above mentioned conditional requirements for pumpingblood, the rate of impeller rotation has a significant effect onstability and structure of sensitive vessels. Impeller rotationaloperation that is not regulated by pump preload pressure will causeatrial suction in sensitive vessels just prior to the pump inlet port,wherein blood vessels collapse when impeller rotation exceeds bloodvessel wall rigidity. Prior art pumping apparatus has not providedadequate integration of controls to insure that rapid adjustments toimpeller rotational speed does not have a negative effect.

Kletschka '005 (U.S. Pat. No. 5,055,005) discloses a fluid pumplevitated by opposing fluid. Stabilization of impeller by opposing fluidalone is not sufficient to maintain impeller in precise position withinpump housing, as well as high pressure fluid jets subject blood to thebefore mentioned blood coagulation caused by mechanical working ofblood.

Kletschka '877 (U.S. Pat. No. 5,195,877) discloses a fluid pump with amagnetically levitated impeller utilizing a rigidly mounted shaftsurrounded by a magnetically levitated rotor which serves as an impellerfor fluid. The shaft of this invention introduces a requirement for ahydraulic bearing and seal at the juncture of the shaft and the rotatingimpeller which subjects blood, or other sensitive fluids, to thermal andstagnation conditions at the region of the bearing.

For more than 25 years, those skilled in the art have studied pumps thatare used as total artificial hearts and experimentally implanted inanimals. These studies have provided useful feedback of the relativeeffectiveness of blood pumping apparatus. These pumps can be categorizeda, producing pulsatile or non-pulsatile flows. The pumps producingpulsatile fluid motion (positive displacement pumps) more closelyresemble fluid motion as provided by the natural heart. Information todate has not yet determined if pulsatile fluid movement is needed toprovide a necessary physiological benefit, or if the pulsatile fluidmotion is primarily due to the non-rotary nature of heart muscle. Mostpulsatile pumps universally require valves (mechanical or tissue) withinherent mechanical problems and limitations. valve systems are notrequired in prior art non-pulsatile pumps, the non-pulsatile pumpsrequire rotating shafts passing through various bearings and seals.These shafts create inherent problems of blood stagnation, contaminationand undesirable thermal conditions, thereby making long term use of thepumps as a replacement for natural heart function unfeasible. Most earlyprior art rotating non-pulsatile systems were installed outside of thebody for short-term cardiac assistance and experienced a moderate amountof success.

One blood pumping apparatus is the total artificial heart. The totalartificial heart has been used in five patients as a permanentreplacement for pathological, irreparable ventricles; and in 300patients as a temporary bridge to cardiac transplantation. The longestsupport on the total artificial heart has been 795 days. Other bloodpumping apparatus, e.g., ventricular assist devices, have been used inpatients unweanable from cardiopulmonary bypass during cardiac surgeryor those whose one ventricle only has failed. The most common mechanicalreplacement of natural heart function is a temporary bridge to cardiactransplantation by a ventricular assist device with over 1250 patientsreceiving such temporary ventricular assist apparatus.

Historically, blood pumping apparatus have presented many problems. Forexample, the pumping mechanism of reciprocating (diaphragm) totalartificial hearts has been energized with gases (pneumatic systems),electricity (motors, solenoids, etc.), and skeletal muscles. The energysources and associated convertor systems possess additional componentsthat increase complexity of the total system and thereby contribute tooverall unreliability. Also, the size of prior art systems for totalartificial hearts is very restrictive to patient mobility and notconducive to quality of life of the recipient. Another constrainingfactor not fully met by prior art apparatus is that the excessive sizeand complexity of energy conversion systems, as well as overall pumpdesign exceeds the available anatomical space. Furthermore, most ofthese prior art reciprocating systems exhibit excessively high (i) noisecharacteristics, (ii) vibration, and (iii) recoil (thrust) levels.

Many of the problems of the prior art rotating pumps have been addressedby those skilled in the art through pump adaptation with capability tomeet the above mentioned requirements for pumping sensitive fluids (suchas blood). These pump adaptations can be accomplished bag support of theimpeller through electromagnets located on the impeller and the housingsuch that the impeller can be rotated without shafts, seals orlubricating systems. Permanent magnets without some form of additionalsupport cannot entirely suspend an object, such as an impeller, butrequire additional adjustable support or force in some axis to achievestabilized suspension. This is based on Earnshaw's theorem whichindicates that suspension systems comprised solely of permanent magnetswill not be stable. However, actively controlled electromagnets can beused to stabilize and support an object with respect to all degrees offreedom of movement. Additionally, one electromagnet with a feedbackposition sensor can provide stable suspension of an object (or impellerin the case of the centrifugal fluid pump). The only expenditure ofenergy in hybrid magnetically supported impellers is electromagneticenergy utilized for stabilizing and rotating the impeller. Permanentmagnets and one electromagnet for impeller suspension and rotationcreate a stable and efficient pump operation.

Within the past decade, prior art patents have disclosed magneticallysuspended and rotated rotors which have exhibited a limited degree ofsuccess. These prior art configurations utilize partial magneticsuspension to reduce hazards to blood. Although magnetically suspendedprior art devices successfully reduce some of the friction hazard of therotary shaft, the prior art devices are still impractical forimplantation in total heart replacement due to size, complexity, andless than optimal impeller positioning, position sensing, and speedcontrol. The excessive size and difficulty in maintaining preciseimpeller positioning and speed of these prior art inventions is duemostly to geometric configuration of the impeller, which is cylindrical,spherical, or otherwise mostly three dimensional in nature.

In view of the foregoing, it would be a significant advancement in theart to provide improvements in magnetically suspended and rotatedcentrifugal pumping apparatus to thereby allow for reduced size andincreased accuracy in impeller positioning and speed controls. It wouldalso be an advancement in the art to provide a centrifugal pumpingapparatus that would be free of shafts, rolling element or fluid filmbearings, mechanical seals, or physical proximity sensors, therebyallowing for a fully integrated pump design without mechanical contact,wear, failure due to seizing up of fluid bearings, and generation ofthrombosis or shear damage. An even further advancement in the art wouldbe to provide a centrifugal pumping apparatus with geometry of impellerand pump housing such as would provide efficient and low-turbulencetransport of fluid throughout pump mechanisms including the pump outputport. Further still, it would be an advancement in the art to provide aversatile centrifugal pumping apparatus that could operate in eitherpulsatile or non-pulsatile mode.

OBJECTS AND BRIEF SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide improvementsin rotating centrifugal fluid pumps for sensitive fluids.

It is another object of the present invention to provide improvements influid pumps using a combination of permanent magnets, efficientnon-contact electromagnetic bearings, and an efficient motor.

It is also an object of the present invention to provide a centrifugalpumping apparatus of relatively compact size to enable anatomicalimplantation.

It is a further object of the present invention to provide a centrifugalpumping apparatus and method to provide a long product life and whichrequires minimal maintenance.

It is an additional object of the present invention to provideimprovements in centrifugal fluid pumps which are used for partial ortotal heart function replacement.

It is still another object of the present invention to provide acentrifugal pumping apparatus and method whose pump design geometryprovides efficient and low-turbulence transport and output of sensitivefluid throughout the pump, including low-turbulence output just beyondthe outlet port.

It is yet another object of the present invention to provide acentrifugal pumping apparatus and method whereby fluid pressure andoutput fluid volume are controlled and changed electronically viaspecific fluid pressure and positioning algorithms.

It is another object of the present invention to provide a centrifugalpumping apparatus and method that is capable of operation in eitherpulsatile or non-pulsatile mode.

It is yet another object of the present invention to provide acentrifugal pumping apparatus and method that is adaptable as either aventricular assist device or paired to provide a total heartreplacement.

The above objects and others not specifically recited are realizedthrough an apparatus and method for a centrifugal fluid pump for pumpingsensitive biological fluids, which includes (i) an integral impeller androtor which is entirely supported by an integral combination ofpermanent magnets and electromagnetic bearings and rotated by anintegral motor, (ii) a pump housing and arcuate passages for fluid flowand containment, (iii) a brushless driving motor embedded and integralwith the pump housing, (iv) a power supply, and (v) specific electronicsensing of impeller position, velocity or acceleration using aself-sensing method and physiological control algorithm for motor speedand pump performance based upon input from the electromagnetic bearingcurrents and motor back emf—all fitly joined together to provideefficient, durable and low maintenance pump operation. A speciallydesigned impeller and pump housing provide the mechanism for transportand delivery of fluid through the pump to a pump output port withreduced fluid turbulence.

These and other objects and features of the present invention willbecome readily apparent from the following description in whichpreferred and other embodiments of the invention have been set forth inconjunction with the accompanying drawings and appended claims.

The underlying rationale for a rotating centrifugal pump with animpeller, fully supported by a combination of permanent magnets andelectromagnetic bearings and rotated by an electric motor, is to preventdamage to blood or other sensitive fluid due to conditions of (1)excessive heat, (2) stagnation, (3) coagulation (thrombosis), or (4)high shear of fluid or blood components (hemolysis) due to fluidinstability caused by turbulence or mechanical working of fluid due toharsh pump mechanism or geometry. Furthermore, the apparatus size ofthis invention is capable of fitting into available anatomical space ifused for total natural heart replacement or ventricular assistance.

To be suitable as a blood pump, the pump must be able to adequately meetphysiological perfusion needs of a ventricular or biventricular assistdevice for total heart replacement. As a total heart replacement device,the pump must be of sufficiently small size and mass to be implantablewithin available anatomical space and not cause any negative effects onsurrounding organs due to excessive apparatus weight. Furthermore, thedisc-like shape of the impeller of this invention significantly reducessize and complexity of the pumping apparatus. The pumping apparatus ofthe invention can be used singularly as a ventricular assist device thatassists or replaces partial heart function or a pair of devices can becombined to form a total mechanical heart replacement. The combined sizeof two devices in a total mechanical heart replacement is approximatelythe size of a natural heart, thereby enabling implantation withinexisting anatomical space.

The impeller of this invention is entirely suspended and enclosed withinits pump housing, thereby providing contact-free operation between pumpimpeller and any other portion of the pump. The pump impeller ismagnetically suspended with a combination of permanent magnets andelectromagnetic bearings. The permanent magnets are configured inreverse polarity which provide positive radial stiffness while beingemployed in the radial gaps inherent in disk-shaped impellers unlike therepulsive permanent magnet rings cited in the prior art patents whichcan only be employed in axial gap configurations. This reverse polaritypermanent magnet configuration is required for a disk-shaped impellergeometry. It is enclosed within its pump housing, thereby providingcontact-free operation between pump impeller and any other portion ofthe pump. The pump impeller is suspended by a combination of permanentand electromagnetic forces. An electric motor rotates the pump impellerto perform the pumping function of fluid. The notable absence of shafts,ball bearings, shaft seals or other sources of contamination makepossible significantly extended product life of the pumping apparatus ofthis invention, thereby enabling long term natural heart replacement.

The pump impeller rotates about an axis and the term “axial direction”is employed here to denote the direction parallel to the axis ofrotation of the pump impeller. The term “radial direction” is used hereto denote directions perpendicular to the axial direction. The inventionconsists of permanent and electromagnetic bearings, comprising magneticand other materials, activated by electrical currents in coils woundaround the bearing magnetic components, which develop axial forces andprovide adjustments to impeller positioning relative to pump housing. Amultiplicity of magnetic bearings, in a suitable configuration arrangedaround the impeller, is required to center the impeller during operationof the pump and to avoid contact between the rotating and stationarycomponents. Six impeller degrees of freedom: three translations andthree rotations, must be controlled. This non-contacting operationallows the bearings to operate without wear or friction losses.

A feedback electronic controller is provided in the suspension system toautomatically adjust the activating (thrust) bearing coil currentswhich, in turn, adjust the control forces exerted by the magneticbearings on the rotating impeller in response to the applied forces.Such electronic controller is continuously provided with an electronicsignal which is related to the position or velocity or acceleration or acombination of position, velocity and acceleration, of the rotatingimpeller in the available clearance space inside the pump frame duringoperation. Switching or direct current power amplifiers and powersupplies necessary to operate the electromagnetic actuators in themagnetic bearings are provided in the invention.

Impeller position and rotational speed of this invention are controlledby specific algorithms which sense fluid pressure and the axial locationof pump impeller within pump housing, correspondingly making adjustmentsto rotational speed and/or impeller position to provide a fullyintegrated system of physiological control. Impeller rotational speed isadjusted to correspond to fluid pressure at pump preload pressure (inletpressure) and/or exit pressure to match bodily needs for increased ordecreased pump flow rate or pressure rise. This also avoids excessiverpm and thus suction thereby avoiding excessive pressure.

The geometric design of the pumping apparatus of this invention providesfluid movement throughout the entire pump mechanism in a smooth,non-turbulent, and low thermal manner. Impeller rotation causes fluid tomove centrifugally by specially curved impeller vanes which emanate fromthe epicenter of the disc-like impeller and extend toward the outside ofthe impeller, and simultaneously create a partial vacuum at the regionnear the impeller's axis of rotation that draws additional fluid intothe inlet port. Blood, or other sensitive fluid, does not stagnate atany location within the pumping apparatus due to return fluid flow alongthe side of the impeller which returns fluid to the impeller epicenterwithout flow interference from stagnation pockets, bearings or seals.Importantly, the geometry of the pump housing, the impeller vanes, theoutlet port, and all other aspects of the pumping apparatus of thisinvention are such that sensitive fluids are protected from damageotherwise caused by stagnation, excessive heat, turbulence, andexcessive mechanical working of the fluid.

The fluid is transported throughout the entire pumping apparatus withoutharsh angular redirection to flow. The configuration of pump housing isdesigned with a spiral volute curve such that the same curve slopethroughout the pump housing enables fluid to be transported within thepump housing with no net abrupt angular change of direction, norcorresponding net increase in thermal friction and energy loss due tofriction from the pump side wall.

Another important feature of the pumping apparatus of this invention isthe capability of operation in either pulsatile or non-pulsatile mode.Cyclic variance of impeller rotational speed will cause the pump tooperate in a pulsatile mode, which more closely resembles pumping actionby the natural heart, whereas uniform impeller rotational speed operatesthe pump in non-pulsatile mode. Operational mode change from pulsatileto non-pulsatile or vice versa is accomplished through changes to thepump operation settings, thereby avoiding trauma associated withreplacing the total pumping apparatus when a change from eitherpulsatile or non-pulsatile is determined to be the preferred operationmode.

One aspect of this invention, unlike prior art devices, is that means orstructure are provided in the magnetic suspension system to generate theelectronic feedback signal related to the position, velocity oracceleration of the rotating impeller either via a physical medium suchas an eddy current, induction, optical, capacitance or other approach,or via a self-sensing electronic signal obtained from the current orvoltage wave form, or a combination of the current and voltage wave formprovided to the activating coils in the magnetic bearings. In the caseof a physical sensor device placed in the pump frame near the clearancegap between the frame and the rotating impeller, the gap between theframe and the rotating impeller, the electronic position, velocity, oracceleration signal, is obtained from signal conditioning electronics.Wiring is provided for input of the signal into the electroniccontroller for the magnetic bearings. In the preferred embodiment, aself-sensing signal is used and the signal conditioning is provided fordetermining the position, velocity, or acceleration of the rotatingimpeller without a physical device, which allows for a minimum number ofwires required in the wiring pathways between the electromagneticactuators and the electronic controllers.

The electromagnetic bearings and their control electronics possess aphysical sensor or self sensing signal such that forces (velocity, oracceleration) attempting to displace the impeller are immediately sensedand the current delivered to the coils is altered, thus avoidingimpeller displacement resultant from those forces.

The flow (cardiac output) of the natural heart is primarily regulated bythe venous return (preload). Another very important feature of theinvention, named the physiologic controller, provides a signal which isused to determine changes in the preload or filling pressure to thepump. The controller sends a signal from monitoring changes in currentflows in the thrust bearing. This information is employed to control therotational speed of the impeller, to regulate pump suction pressure, andto regulate the needed pump outputs. This unique feature of themagnetically suspended pump allows for sensing of the inflow pressure(preload) and thus the flow (cardiac output) consistent with thephysiologic needs of the recipient as a ventrical assistance device(VAD). When two pumps are used as a total artificial heart (TAH) therotational speed of each pump will be regulated independently and eachpump will be sensitive to the preload thus providing changes in flow andbalance consistent with the changing physiologic needs of the recipient.This feature allows the pumps to be used without the need of thecomplexities associated with volume displacement chambers required withpulsatile pumps.

The invention provides for a motor to impart the necessary torque androtation to the rotor. This is a three phase brushless DC motorcontrolled by using back EMF. The motor is in the shape of a disclocated in the base of the housing frame and near the center of rotationof the impeller. Commutating the motor with back EMF allows effectivestart-up and precise control of the speed of rotation. Changes in therotation speed are predicated on the preload as described above in theform of a physiologic controller.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the inventionwill become apparent from a consideration of the following detaileddescription presented in connection with the accompanying drawings inwhich:

FIG. 1 is a perspective view of the magnetically supported and rotatedpumping apparatus of this invention;

FIG. 2 illustrates an exploded side view of a pumping apparatus fullysupported by one electromagnetic bearing and a plurality of permanentmagnets, and rotated by an electric motor of this invention;

FIG. 3 is a cross-sectional view of FIG. 1 taken along line 3—3;

FIG. 4A is a plane view of FIG. 3 taken along line A;

FIG. 4B is a cross-sectional view of FIG. 3 taken along line A;

FIG. 5A is a plane view of FIG. 3 taken along line B;

FIG. 5B is a cross-sectional view of FIG. 3 taken along line B;

FIG. 6A is a plane view of a preferred embodiment of FIG. 3 taken alongline C;

FIG. 6B is a cross-sectional view of FIG. 3 showing a preferredembodiment of a motor stator;

FIG. 7A is a plane view of FIG. 3 taken along line C;

FIG. 7B is a side view of a portion of the impeller in FIG. 3;

FIG. 8 is an enlarged, fragmentary, cross-sectional view of the pumpimpeller and housing of FIG. 1;

FIG. 9 is a perspective view of the pump impeller of this inventionshown in semi-transparent mode for clarity;

FIG. 10 is a cross-sectional view of the pump impeller taken along linesA—A of FIG.9;

FIG. 11 is a front view of the pump impeller, taken along lines B—B ofFIG. 9, with shroud assembly removed;

FIG. 12 illustrates the coordinate system and the symbols for the sixdirections of magnetic actuation for the pump of the present invention;

FIG. 13A shows electronic circuits that provide electronic feedback forcontrol of the impeller position within the stator clearance region;

FIG. 13B shows further details of the electronic circuits of FIG. 13Bthat provide electronic feedback for control of the impeller positionwithin the stator clearance region;

FIG. 14 illustrates electronic filters from a self sensing part of theinvention, the filters extracting fluid gap dimension information whileremoving the effects of power supply voltage, switching frequency, dutycycle variation, and electronic or magnetic noise;

FIG. 15 illustrates a table of graphs of the signals as they passthrough the filters of FIG. 14;

FIG. 16 depicts a schematic diagram of an integrator circuit whose gainis controlled by an analog multiplier indexed to the estimated gap;

FIG. 17 shows a schematic diagram of a physiological electronic feedbackcontrol circuit based on motor current and speed;

FIG. 18 shows a schematic diagram of a physiological electronic feedbackcontrol circuit based on bearing current; and

FIG. 19 shows a physiological electronic feedback control circuit forregulating the motor speed relative to preload and afterload signals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The presently preferred embodiments of the present invention will bebest understood by reference to the drawings, wherein like parts aredesignated by like numerals throughout. It will be readily understoodthat the components of the present invention, as generally described andillustrated in the figures herein, could be arranged and designed in awide variety of different configurations. Thus, the following moredetailed description of the embodiments of the apparatus, system, andmethod of the present invention, as represented in FIGS. 1 through 19,is not intended to limit the scope of the invention, as claimed, but ismerely representative of presently preferred embodiments of theinvention. Reference will now be made to the drawings in which thevarious elements of the present invention will be given numeraldesignations and in which the invention will be discussed so as enableone skilled in the art to make and use the invention. It is to beunderstood that the following description is only exemplary of theprinciples of the present invention, and should not be viewed asnarrowing the appended claims.

Elements of construct 10 are operable in singular mode as a ventricularassist device, or paired for a total artificial heart. In the case ofthe total artificial heart which utilizes two of construct 10, eachconstruct 10 operates entirely independent of the other construct,thereby eliminating complex control equipment and circuits that wouldotherwise be required if both constructs were combined.

The physiologic controller (not shown) senses fluid pressure insideintake vessel 19 and generates an electrical signal to modify rotationalspeed of motor 40 according to specific algorithms determined byelectronic controller (not shown). The physiologic controller may signala change in rotational speed of motor 40 to compensate for a change influid pressure inside intake vessel 19 yet avoid excessive rotationalmotor speed that would collapse vessels. In addition to controllingrotational speed of motor 40, the physiologic controller (not shown)senses position, velocity, and/or acceleration information of impeller21 via eddy current, induction, optical, capacitance or otherself-sensing electronic signals and generates an electrical signal thatis sent to the electronic controller (not shown), which correspondinglyprovides adjustment to electrical current in electric activation coils44 and 48, thereby providing adjustment to control forces exerted byelectromagnetic thrust bearings 46 and 50. Adjustments toelectromagnetic thrust bearings 46 and 50 compensates for applied forcesdue to fluid, motor forces, gravitational load, acceleration forces, andother incidental forces.

The rotation of impeller 21 brings impeller vanes 26 in contact withfluid to be pumped, thereby causing fluid to move radially toward spiralvolute exit 18. The centrifugal transport of fluid from the region atthe axial center of construct 10 toward the spiral volute exit 18correspondingly creates a partial vacuum at the region of impellerintake opening 30 and draws in additional fluid through intake vessel19. The unique logarithmic spiral configuration of spiral volute exit 18then transports sensitive fluid along the region near the circumferenceof construct 10 in a smooth, non-turbulent and low thermal manner tooutlet vessel 15. Outlet vessel 15 is connected to anatomical vessels orother mechanisms.

A portion of fluid pumped by impeller 21 returns from the region of highpressure near spiral volute 18 along both sides of impeller 2l, viafirst impeller return chamber 32 and second impeller return chamber 34,in the form of reverse fluid flow to the region of lower pressure nearimpeller intake opening 30. Fluid returning along second impeller returnchamber 34 also passes through impeller return opening 36, and therebyserves to equalize internal fluid pressures and prevent flow in theclearance passages from sensitive fluid stagnation.

If construct 10 is to be operated in pulsatile mode, rotational speed ofimpeller 21 is varied and controlled by the electronic controller (notshown), which adjust electrical current in motor 40, therebyaccelerating and decelerating the rotation of impeller 21 and causingfluid to be pumped in a pulsatile fashion.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

Referring now to FIG. 1, the magnetically suspended and rotatedcentrifugal pumping apparatus of this invention is shown generally asconstruct 10. Construct 10 is configured with a first pump housing half12 and a second pump housing half 14, together with hermetic seal 28, toform the confines for enclosure of the remainder of the pumpingcomponents, discussed in detail hereafter. The electronic controller andbatteries or other power source for operation, though necessary foroperation, are not shown. Construct 10 is configured with one or morepump inlet vessels, shown in FIG. 1 with one inlet vessel 19 as thepreferred embodiment. Pump inlet vessel 19 is seamlessly formed andintegral to first pump housing half 12 and includes an inlet throughbore20 which provides containment for fluid entering pump construct 10.Fluid enters pump construct 10 via pump inlet vessel 19, which providescontainment and delivery of fluid by inlet flow throughbore 20, to aregion proximate to the axial center of pump construct 10. Outlet vessel15 is located tangentially from the outside diameter of construct 10 andis formed by the combining of first pump housing half 12 and second pumphousing half 14 with containment walls forming pump outlet throughbore16 and sealed by hermetic seal 28. It will be appreciated by those ofskill in the art that the inlet or inlet vessel 19 and the outlet oroutlet vessel 15 may be integral with either housing half 12, 14 or maybe a separate member attached to the first or second housing half 12, 14by ways known in the art such as bonding or welding.

FIG. 2 illustrates an exploded side view of the magnetically supportedand rotated pumping apparatus of this invention. The exploded view showsthe pump inlet 19, the first pump half 12, a bearing target 100 having apermanent magnet set 56, an impeller shroud 22, an impeller hub 24, animpeller inlet 112, permanent magnets 52 and 57, an impeller vane 116, amotor rotor 120 having a permanent magnet set 59, permanent magnets, 54and 58, the outlet vessel 15, and the pump outlet throughbore 16. Alsoshown in FIG. 2 is a combined axial thrust, moment, and radial bearinghousing 124 and a combined axial thrust, moment, and radial bearinghousing 126.

Referring to FIG. 3, spiral volute exit 18 is formed by the combinationof first pump housing half 12 and second pump housing half 14, andsealed by hermetic seal 28. Importantly, the configuration of thelogarithmic spiral volute exit 18 of this invention utilizes a spiralvolute curve formation to eliminate abrupt or harsh changes of directionto fluid flow during transportation from impeller to outlet vessel 15,thereby avoiding damage to sensitive fluids as described herein before.The combination of first pump housing half 12 and second pump housinghalf 14, together with hermetic seal 28, also forms containment forinternal impeller 21 and impeller chambers 27 a, 27 b, 27 c, and 27 d(see FIG. 9), discussed hereafter in detail. Fluid flows entirely aroundimpeller 21 via first return flow chamber 32 and second return flowchamber 34.

FIG. 3 also shows an embodiment of a motor 40 that controls therotational speed of the impeller 21. Magnetic fields allow the motor 40to be in rotational engagement with the impeller 21.

FIGS. 4A and 4B depict a portion of the pump 10. FIG. 4A shows a planeview of section 4B (see FIG. 3) of the second pump housing half 14 andFIG. 4B shows a side view of section 4B of FIG. 3. Windings (or controlcoils) 52 and a bias coil 53 are shown that enable construction of thepump 10 by those skilled in the art. Axial thrust bearing function whichis controlled by an electronic controller.

FIGS. 5A and 5B depict another portion of the pump 10, however, FIG. 5Ashows a plane view of section 5B (see FIG. 3) of the first pump housinghalf 12 and FIG. 5B shows a side view of section 5B of FIG. 3. Onceagain, windings (or control coils) 52 and a bias coil 53 are shown thatenable construction of the pump 10 by those skilled in the art. Thiscombination performs an axial thrust bearing function which iscontrolled by an electronic controller.

FIGS. 6A depicts section 6B of FIG. 3 in plane view to demonstrate thewindings 84, and FIG. 6B shows a preferred embodiment of the stator 80of the motor 40. The motor 40 will be described in greater detailhereinafter.

FIG. 7A depicts section 6B of FIG. 3 in plane view to show the rotor orimpeller 21 portion of the motor 40 and to demonstrate the arrangementof the permanent magnets 92 on the rotor. The magnets 92 are arcuatelyarranged and alternate north pole 91, south pole 93, north pole 91,south pole 93, etc. until the circular arrangement depicted in FIG. 7Ais accomplished. It will be appreciated that the arcuately shapedmagnets 92 may include any number of generally curved surfaces or lines.

FIG. 7B shows the same portion of the impeller (or rotor) 21 incross-section. Also shown in both FIG. 7A and 7B is the permanent magnetring 54, the permanent magnetic ring set 59, and magnetic material 55that is the target of the axial thrust bearing. The rotor 21 will bedescribed in greater detail hereinafter.

FIG. 8 is an enlarged, fragmentary cross-sectional view of the pumpimpeller and housing of FIG. 1. FIG. 8 focuses on a portion of thecross-section view shown in FIG. 3 and provides greater clarity to thedisclosure discussed relative to FIG. 3.

Pump impeller 21 is configured with two or more impeller vanes 26 a, 26b, 26 c, and 26 d, shown in FIG. 9, with a preferred embodiment of fourimpeller vanes 26 a, 26 b, 26 c and 26 d. Each impeller vane 26 ismounted between impeller shroud 22 and impeller hub 24 such thatimpeller chambers 27 a, 27 b, 27 c and 27 d are formed. Each impellervane 26 a, 26 b, 26 c, and 26 d corresponds to impeller chambers 27 a,27 b, 27 c, and 27 d respectively.

Referring to FIGS. 9, 10, and 11, impeller vanes 26 are configured witha spiral curvature such that rotation of impeller 21 brings impellervanes 26 in contact with fluid to be pumped, thereby causing fluid tomove radially toward spiral volute exit 18. Rotation of impeller 21centrifugally transports fluid from the region at the axial center ofconstruct 10 toward the spiral volute exit 18, correspondingly creatinga partial vacuum at the region of impeller intake opening 30 and drawingin additional fluid through intake vessel 19 (FIG. 1). Specifically, asshown in FIG. 11, the impeller is designed to allow for a smoothtransition of the flow vector from inlet to outlet. This is accomplishedin one particular embodiment employing a blade angle of 17.degree. atthe base of the blade at the inlet, A. The blade angle is graduallydecreased to 11.degree. at the top of the blade at the inlet, B. Hencethe blade is not straight in the axial direction near the inlet. Theblade gradually transitions to being straight in the axial directionwith an angle of 37.degree. near the midpoint of the blade, C. This37.degree. angle is maintained to the exit point, D. All blade anglesare the inner angles of the blade relative to a tangent to a circlecentered in the center of impeller 21. Referring to FIG. 2, the pumpvolute is located in pump stationary component to provide a smooth flowof pumped fluid from the discharge of the impeller at relatively highvelocity into the pump exit passage where it is slowed down prior toexiting from the pump. The volute increases the fluid pressure (head) byconverting fluid kinetic energy (velocity) to potential energy (pressureor head).

The clearance around the impeller 21 in one particular embodiment ismaintained at 0.030″ to allow for good washing of the surfaces. Anychanges in direction of the flow in the clearance passages are made bymaximizing the radius of curvature in order to keep the flow laminar.

Referring again to FIGS. 3 and 8, in one embodiment, a portion of fluidpumped by impeller 21 returns from the region of high pressure nearspiral volute 18 along both sides of impeller 21, via first impellerreturn chamber 32 and second impeller return chamber 34, as reverse flowto region of lower pressure near impeller intake opening 30. Fluidreturning along second impeller return chamber 34 also passes throughimpeller return opening 36, and thereby serves to equalize internalpressure. The width of impeller return chambers 32 and 34 are calculatedby a precise balance of primary fluid flow and reverse flow, such thatfluid does not stagnate within the pump but also does not possessunnecessary inefficiencies.

Pump impeller 21 is suspended within its pump housing by permanentmagnet sets 52, 54, 56, 57, 58, and 59 in combination electromagnets 44,46 and 48, 50. Permanent magnet set 52 is a magnetic ring located at thepractical circumference edge of impeller shroud 22 and is oriented withnorth poles proximal and south poles distal thereby utilizing themagnetic repulsive forces away from interior wall of first pump half 12.Correspondingly, permanent magnet set 54 is it magnetic ring located atthe practical circumference edge of impeller hub 24, and is orientedwith north poles proximal and south poles distal thereby utilizingmagnetic repulsive force away for interior wall of second pump housing14, but whose direction of force opposes permanent magnet set 52, suchthat impeller 21 is stabilized axially at the circumference of impeller21.

First housing permanent magnet set 56 and first impeller permanentmagnet set 57 are configured in a double ring configuration locatedproximal to impeller intake opening 30, with alignment on either side offirst return flow chamber 32, and are integral to first pump housinghalf 12 and impeller shroud 22, respectively. The reverse polarity offirst housing permanent magnet set 56 and first impeller permanentmagnet set 57 for each of the two magnetic rings, enables radialstabilization and, due to the angular positioning, also provides adegree of translational stabilization of impeller 21.

Second housing permanent magnet set 58 and second impeller permanentmagnet set 59 are configured likewise in a double ring configuration andare proximal to return opening 36, with alignment on either side ofsecond return flow chamber 34, and are integral to second pump housinghalf 14 and impeller shroud 24, respectively. The reverse polarity ofsecond housing permanent magnet set 58 and second impeller permanentmagnet set 59 enables radial stabilization of impeller 21 and a degreeof translational stabilization of impeller 21.

The double ring configuration of the magnetic sets is a double magnetreverse polarity design. The magnetic sets 56, 57, 58, and 59 are eachlocated at approximately one-half the radial point of the impeller 21.The rings of each set are placed in an attractive orientation next toone another and the sets are placed in a reverse polarity from oneanother. Thus, the magnetic arrangement has the property of producingpositive radial stiffness. If a fluid or other force tends to push theimpeller 21 off center, the attractive forces between the NS and SNrings apply a radially centering force to prevent it. For the geometryand magnetic strength described herein, the radial stiffness isapproximately 67,000 N/m. The two bearing sets have a combined radialstiffness of 134,000 N/m. This double ring arrangement has been shown tokeep the impeller properly centered and operating during ventricularassist duty.

It is important to note that the four sets of permanent magnet rings 56,57, 58 and 59, as described above, provide a significant portion of thetotal suspension and stabilization of impeller 21 within pump housinghalf 12 with final stabilization, fine positioning and rotation ofimpeller 21 provided by electromagnetic thrust bearings 46 and 50,electric activation coils 44 and 48 and motor 40 with associated coilsat 42 and 60. The magnetic suspension system and rotation of impeller 21provides a contact-free operation which increases overall product lifeand reliability and avoids sensitive fluid damage as discussedhereinbefore. The four magnetic rings as described above, each withreversed North and South magnetic polarities, are configured such thatinteracting magnetic fields produce positive radial and axial stiffness,which are necessary to counter radial and axial applied forces due tofluid, motor forces, gravitational load, acceleration forces, and otherincidental forces.

Electromagnetic thrust bearings 46 and 50 are comprised of stationarymagnetic actuator components, electric activation coils 44 and 48,electronic controllers (not shown), power amplifiers (not shown), asensor or other means of sensing impeller 21 position, velocity oracceleration (not shown). In summary, the respective actuators which areindividually controlled enable control of the identified six axes.

An electronic controller (not shown) provides automatic adjustment toelectrical current in electric activation coils 44 and 48, which changein electrical current adjusts the control forces exerted byelectromagnetic thrust bearings 46 and 50. The electronic controllercontinuously provides electric signal input which relates to position,velocity and/or acceleration of the rotating impeller 21. Additionalcomponents necessary for operation of construct 10 are switching ordirect current power amplifiers and power supplies (not shown).

As stated above, FIGS. 6A and 6B show a plane view and a cross-sectionview of a motor stator 80 of the motor 40. Motor 40 is a 3-phasebrushless motor and provides electromagnetic force to start and rotatethe pump impeller or rotor 21 including an arcuately shaped rotor disksuspended with single sided flux gap. As will be appreciated by those ofskill in the art, the shape of the rotor disk and blades maybe shapedother than arcuately and still practice the teachings of this invention.For example, the disk and/or blades may include generally curvedsurfaces or lines as well as straight surfaces. As shown in theembodiment of FIGS. 7A and 7B, the motor 40 consists of a permanentmagnet rotor 21 with permanent magnets 92 imbedded in the hub of acentrifugal or mixed flow pump. The magnets 92 are wedge shaped andarranged to form a circular rotor. The magnets 92 are arranged such thatmagnetization of the permanent magnets alternate north and southpolarities both radially and angularly around the rotor 21. Referring toFIGS. 6A and 6B, the motor stator 80 has wire windings 84 excited bycurrent from an electronic controller. This stator arrangement producesa magnetic field interacting with the permanent magnets 92 to produce atorque on the rotor 21.

Although the motor stator 80 can be suspended in at least threeconfigurations depending on torque, speed, and bearing requirements, theconfiguration of FIGS. 6A and 6B shows an ironless configuration for themotor stator; stator 80 has no saturable magnetic material. As shown inFIG. 6B, wire 84 is wound on a separate fixture and fixed in place onrotor 80 using epoxy or similar material.

The above configuration meets the unique criteria for a centrifugal ormixed flow medical device pump that is needed as was discussed in thebackground section. The use of permanent magnets in the rotor as part ofa magnetic system results in no mechanical contact between the rotor andstator of the motor. The electromagnetic bearing sets 52, 54, 56, 57, 58and 59 in the magnetic system allow the rotor/impeller 21 to rotate withcomplete lack of contact with the stator 80. The geometry of the motormeets the requirements of allowing the motor to drive the pump in anefficient manner while providing for laminar flow in the gaps betweenthe impeller and housing, with minimal stagnation of blood. This isrealized by keeping bending radii large.

FIG. 12 shows the coordinate system for defining impeller 21 magneticactuation in the required six directions: three translations (x,y,z) andthree rotations (.PHI., .psi., .theta.). All three translationaldisplacements (x,y,z) and two rotations (pitching motions about twoaxes) (.PHI., .psi.) are held nearly fixed in space relative to thestator by the magnetic forces. The last rotation actuation (.theta.),about the z axis rotation, is accomplished by the motor. In summary,FIG. 13 discloses six axes of control, including (i) one axialtranslational axis, (ii) two radial translational axes, and (iii) threerotational axes comprising two axes controlled for moment and one axiscontrolled by motor rotation. It will be appreciated by those of skillin the art that the position of the impeller 21 may be controlled bycontrolling various combinations of translational, radial, or rotationalaxes. For example, in one embodiment, the six axes of control mayinclude one axial translational axis, one rotational axis controlled bymotor rotation, and a pair of axes controlled for moment at respectiveends or sides of the impeller.

In a preferred embodiment, the magnetic bearings are constructed in twoparts: 1) a thrust/moment configuration and a 2) radial/thrustconfiguration. Although numerous arrangements could be used to form afour quadrant actuator, in this embodiment, unlike an allelectromagnetic embodiment, permanent magnets are used with theactivation coils and are placed in pairs so that there are fourquadrants of control. This provides a combination of axial actuation (z)and pitching moments (.PHI., .psi.) The thrust force (z) is generated sothat each magnetic pole in the arrangement exerts the same force on thetarget. The pitching angular actuation forces (moments) are alsoproduced by the permanent magnets above and below the impellercenterline (.PHI. angular displacement) and to the left and right of theimpeller (.psi. angular displacement). The function of the electroniccontroller is to determine what combination of currents must be employedto fine tune these axes, i.e., provide final stabilization and finepositioning and rotation. The axial thrust bearings are the onlyelectronically controlled bearings in this embodiment of the invention.

Second, this magnetic bearing configuration can exert control forces inthe axial direction (z), radial directions (x,y), and angulardisplacements (.PHI., .psi.). These two magnetic bearing configurations,the thrust/moment and the radial/thrust configurations, produce thenecessary magnetic forces and moments required to keep the impellercentered and under control.

FIGS. 13A and 13B show an embodiment of the electronic circuits forelectronic feedback control of the impeller position within the statorclearance region. In the preferred embodiment, these electronic circuitsapply to the axial thrust bearing only because the axial thrust bearingis the only set of coils electronically controlled. Electronic circuitscomposed of resistors, capacitors, amplifiers, etc. are combined tocontrol the impeller dynamics using proportional-integral-derivativecontrol methods or other linear control algorithms such as state space,mu synthesis, linear parameter varying control, and nonlinear controlalgorithms such as sliding mode control. Particular control algorithmsare used to take into account impeller rigid body gyroscopic forces,fluid stiffness, damping and inertia properties whose magnitude dependupon impeller position, rotational rate, pressure rise, and flow rate.In one embodiment, the physical circuits are miniaturized using surfacemount technology, very large scale integrated (VLSI) circuit design andother means.

In the embodiment shown here, the control algorithm produces the eightcoil currents which control the three displacements (x,y,z) and twoangular displacements (.PHI., .psi.) The controller algorithm design isrobust to account for uncertainties in forces acting on the impellersuch as fluid stiffness, damping and inertia properties, gyroscopiceffects, magnetic forces, etc. The control algorithms are implemented ona dedicated microprocessor with adjustable parametric variationimplementation to account for different physiological needs for thedifferent applications to different size humans, from children to largeadults.

Power amplifiers are employed in the invention to produce the desiredcoil currents for the electromagnetic bearings as determined by theelectronic controller output voltage. One embodiment of a switchingamplifier, operating with voltage switched either on or off at afrequency much higher than the rotational frequency of the pumpimpeller, is utilized in the device because power amplifiers are veryefficient, having an efficiency in the range of 85 to 99%. Theelectronic power circuits are composed of magnetic coils, withassociated resistance and inductance, resistors, capacitors,semiconductor components. The coils are implemented using wire with lowresistance.

These power circuits are designed to be regenerative—that is, themagnetic bearing enabling power moves back and forth between themagnetic coil inductors to the capacitors with the only losses occurringdue to the low coil resistance (ohmic losses). The high power present inthe magnetic coil circuits is a small fraction of the nominal powercapability; the nominal power capability being defined as supply voltagetimes average switched current in the coils. With these low powerswitching amplifiers and regenerative coil power circuits, theundesirable heating of the blood is kept to a minimum.

The invention is designed to generate the electronic signal related tothe position, velocity or acceleration of the rotating impeller throughone of the following: (i) a physical device such as an eddy current,induction, optical, capacitance or other approach; or (ii) a combinationof the current and voltage waveform provided to the activating coils inthe magnetic bearings. In the case of a physical sensor device placed inthe pump frame near the clearance gap between the frame and the rotatingimpeller, the electronic position, velocity, or acceleration signal, isobtained from signal conditioning electronics and wiring provided forinput of the signal into the electronic controller for the magneticbearings.

In the case of a self-sensing signal, the signal conditioning isprovided for determining the position, velocity, or acceleration of therotating impeller without a physical device, which allows for a minimumnumber of wires required in the wiring pathways between theelectromagnetic actuators and the electronic controllers.

A preferred embodiment of the sensing function of the invention is theself sensing configuration. The self sensing configuration avoids theuse of a physical sensor in the stator, minimizes the size of the pump,and minimizes the number of wires required for operation. In oneembodiment illustrated in FIGS. 13A and 13B, position sensing isaccomplished by examining the voltage and current switching wave forms(employed with the switching power amplifiers described above forseveral of the electromagnetic coils. Each coil is driven by a switchingpower amplifier with a high (in the kHz range) carrier frequency. Theresulting current waveform, one version which is shown in FIG. 15, is acombination of the relatively low frequency commanded waveform (toproduce the necessary control force for positioning the impeller) and ahigh frequency triangular waveform due to the high frequency carrier.The amplitude (magnitude) of this commanded waveform is a function ofthe circuit inductance (a combined inductance due to the magneticmaterial properties in the magnetic bearing and due to the fluid gap),the switching frequency, the power supply voltage, and the duty cycle ofthe switching amplifier (ratio of on to off voltage employed inamplifier to produce the desired control forces).

FIG. 14 shows an embodiment of electronic filters that are provided inthe self sensing part of the invention to extract the fluid gapdimension information while removing the effects of power supplyvoltage, switching frequency, duty cycle variation, and electronic ormagnetic noise. A parameter estimation method is employed to demodulatethe signal and determine the fluid gap dimension. One embodiment of theenvelope of filters is employed, consisting of a high pass filter toremove the bias current, a precision rectifier to make the waveformstrictly positive, and a low pass filter to remove the variation in theremaining signal. The embodiments shown in FIG. 14 gives a low noisesensor with a high bandwidth, suitable for the self sensing signaldetermination of the fluid gap dimension.

FIG. 18 shows the sequence of signal forms as they pass through thefilters: the graph at 180 shows the supply coil voltage, the graph at182 shows a typical actual coil current waveform, the graph at 184 showsthe current signal output from the integrator (described in detail inFIG. 19) which removes the change in coil current due to the control ofthe externally imposed forces and moments, the graph at 186 shows therectified version of 184, and the graph at 188 shows the time average of186 extracted using a low pass electronic filter.

FIG. 19 shows a circuit which extracts the change in coil current due tothe control of the externally imposed forces and moments. This is shownin the preferred embodiment of a negative feedback circuit, whichcomprises an integrator whose gain is controlled by an analog multiplierindexed to the estimated gap. This feedback circuit includesproportional-integral device where the estimated displacement and theintegral of the estimated displacement are combined to form the negativefeedback signal and then compared to the original voltage waveform toprovide the desired current waveform r m proportional to the impellerdisplacement.

In this application, because of the permanent magnet arrangement, biascurrents are not created that will produce high heat generation. Biascurrent is not desirable for use in human sensitive fluids such asblood. The axial thrust bearing is the one set of coils that uses theself sensing electronic controller and thus, hardware, circuitcomplexity, and wiring are all reduced along with the reduction in heatfrom bias currents.

The use of pumps for sensitive applications often requires adjustment offlow rates and pressure rises such as in the artificial heart where thephysiological conditions change significantly. The rotational speed mustnever be so high as to cause excessive suction that can lead to inflowvessel collapse. For example, the body may be resting or sleeping with arather low required flow rate and pressure rise whereas if the body isundergoing exercises, such as walking, a much higher flow rate andpressure rise is required. In one embodiment, the primary method ofadjusting the flow rate and pressure rise is by varying the motor speed.In addition to the motor, the axial thrust bearings are the only set ofcoils (or magnetic forces) that are electrically controlled. Thus,although quadrants are unnecessary and the preferred embodiment does nothave quadrants, the invention could use quadrants when additional momentcontrol is desired or required.

A second embodiment of the physiological controller uses an indirectmeasurement of pressure rise from the inlet of the pump to the outlet ofthe pump (i.e., Pout-Pin). At a given flow rate, changes in pressureacross the pump are an indication of changes in systemic resistance inthe circulation system of the patient. Change in systemic resistance isknown to be one indicator of increased physical exertion in humans.Thus, a measurement of pressure difference from outlet to inlet is usedas a basis for a physiological controller.

The measurement of pressure difference from inlet to outlet can beindirectly measured by two methods which are (1) measurement of motorcurrent and pump speed, or (2) measurement of bearing current, or somecombination thereof. In physiological applications, the pump inletpressure is called the preload while the pump exit pressure is calledthe afterload.

The first method to measure pressure indirectly uses measurements ofmotor current and pump speed. These measurements are used in anelectronic controller to derive pressure based on equations and/ortables electronically stored in the controller. The relationship betweencurrent, speed, and pressure rise is characterized and calibrated priorto operation, providing the basis for the controller. The block diagramfor the implementation of the controller is shown in FIG. 20.

The second method to measure pressure rise indirectly uses magneticbearing current. It is well known that current in an active magneticbearing is directly proportional to force on the rotor. The pressuredifference from outlet to inlet of the pump can be derived directly fromthe resultant net force on the impeller due to the pressure difference.Hence, the bearing current can be used in an electronic controller toderive the pressure difference from outlet to inlet of the pump. Theblock diagram of the implementation of the controller is shown in FIG.18.

FIG. 19, shows another embodiment of a physiological electronic feedbackcontrol circuit that is provided in the invention to regulate the motorspeed relative to the preload and afterload signals thereby properlycontrolling the motor speed. The physiological control circuit isprovided to regulate the pump flow rate and pressure rise to meet thephysiological needs of the biological application. Reference number 220indicates an interface between the physiological controller and themotor commutator such that a desired speed signal is sent to the motorcommutator and an actual speed signal is sent to the physiologicalcontroller via voltage represented by the arrow in FIG. 22 designated as“Sensed Back EMF”. Thus, the embodiment of FIG. 19 illustrates motorcontrol based on physiological parameters.

In addition to electronic signals relating to the preload and afterloadforces internal to the pump, the electronic signals from the activatingcoil currents in the electromagnetic bearings are related to otherforces such as the gravitational loading and acceleration effectsrelating to the beginning of motion and the stopping of motion. Also,electronic signals related to the acceleration are obtained by sensing,either in the pump housing or other location of known position relativeto the pump, the acceleration in one, two, or three orthogonaldirections. The electronic acceleration signals are then employed in theinvention to subtract that signal from the preload and afterloadsignals, as described above. The resulting difference signal is thenused for the physiological controller described above.

The speed of the motor is related to the physiological performance ofthe pump. The motor feedback emf is used to sense the rotational speedof the motor rotating about the pump impeller axis and to develop anelectronic signal proportional to the impeller rotational speed. Theimpeller rotational speed signal is provided to the electronicphysiological feedback controller described above. The present motorrotational speed is used in combination with the preload and afterloadsignals to adjust future motor speeds to match physiological pump flowrate and pressure rise needs based upon body requirements and to avoidundue suction.

The present invention may be embodied in other specific forms withoutdeparting from its structures, methods, or other essentialcharacteristics as broadly described herein and claimed hereinafter. Thedescribed embodiments are to be considered in all respects only asillustrative, and not restrictive. The scope of the invention is,therefore, indicated by the appended claims, rather than by theforegoing description. All changes that come within the meaning andrange of equivalency of the claims are to be embraced within theirscope.

What is claimed and desired to be secured by United States LettersPatent is:
 1. Apparatus for pumping sensitive biological fluidscomprising: a construct having an exterior, a hollow interior havingwalls therein, at least one housing permanent magnet disposed therein,and an axial center; an inlet for passage of fluids through theconstruct and into the hollow interior of the construct; an outlet forpassage of fluids through the hollow interior of the construct; animpeller disposed within the hollow interior of the construct and out ofcontact therewith for controlling fluid flow through the hollow interiorof the construct; a plurality of magnetic actuators which provide sixaxes of control, including one axial translational axis, and onerotational axis; at least one impeller permanent magnet juxtaposed tothe housing permanent magnet for suspending the impeller out of contactwith the hollow interior of the construct; a motor for selectivelyrotating the impeller to thereby control fluid flowing through theapparatus, and wherein at least one of the five axes controlled formoment axial translation and radial translation is controlled by a setof permanent magnets and wherein the set of permanent magnets ismagnetized in an axis parallel to an axis of rotation of the impeller.2. The apparatus of claim 1, wherein the inlet is integral with theconstruct exterior.
 3. The apparatus of claim 1, wherein the outlet isintegral with the construct exterior.
 4. The apparatus of claim 1,wherein the outlet is radially located from the axial center of theconstruct.
 5. The apparatus of claim 1, wherein the impeller comprisesarcuate blades.
 6. The apparatus of claim 1, wherein the impellercomprises arcuate passageways whereby fluid flow through the constructis gradually redirected from the inlet to the outlet.
 7. The apparatusof claim 1, wherein at least one of the magnetic actuators is anelectromagnet.
 8. The apparatus of claim 7, wherein the magneticactuators comprise a plurality of electromagnets.
 9. The apparatus ofclaim 1, wherein at least one of the five axes controlled for momentaxial translation and radial translation is controlled by a set ofpermanent magnets attached to the housing.
 10. The apparatus of claim 9,wherein the impeller comprises an integrated combination of an impellerfor fluid flow through the construct and a rotor being controlled by themotor thereby allowing the motor to control rotation of the impeller,the integrated combination of the impeller and the rotor forminginterior sides of a first return flow chamber and a second return flowchamber, respectively, for permitting fluid flow around the suspendedimpeller.
 11. The apparatus of claim 10, wherein the interior side ofthe rotor forming the second return flow chamber includes a secondmember having a curvature corresponding to a curvature of walls of thehollow interior of the construct, the second member being coupled to afirst member by impeller wherein impeller chambers are formed from (i)the arcuate blades, (ii) the first member, and (iii) the second member,thus forming the arcuate passageways for the gradual redirection offluid from the inlet to the outlet.
 12. The apparatus of claim 11,wherein the second member includes a second magnetic material forinteraction with a second electromagnetic thrust bearing and a secondelectric activation coil, wherein the second electromagnetic thrustbearing and the second electric activation coil stabilizes the impellerand controls a combination of two degrees of freedom in radial position,axial position, external radial forces, and external thrust forces whichact upon the impeller.
 13. The apparatus of claim 11, wherein the secondmember comprises a rotor integrally formed therein and the rotor havinga plurality of permanent magnets disposed thereon for interaction withthe motor wherein the rotor may be rotated by the motor and therebyrotate the impeller.
 14. The apparatus of claim 1, further comprising apositioning structure for controlling six axes of impeller motion, saidpositioning structure including a hybrid magnetic bearing system whereina first impeller permanent magnetic bearing set and a first housingpermanent magnetic bearing set each comprise at least one permanentmagnet ring situated about the impeller and the housing, with polaritiesarranged so that positive radial stiffnesses are generated, such thatthe impeller operates in a centered position relative to the two radialdisplacements for control of two of the six axes.
 15. The apparatus ofclaim 14, wherein a first impeller magnetic target set and the firsthousing electromagnetic bearing set comprise electromagnetic bearingswhich control the remaining axial displacement and two angulardisplacements of the six axes so that the impeller operates in acentered position with regard to the axial and two angular axes.
 16. Theapparatus of claim 1, further comprising a positioning structure forcontrolling six axes of impeller motion, said positioning structureincluding a hybrid magnetic bearing system wherein a first impellerpermanent magnetic bearing set and a first housing permanent magneticbearing set each comprise at least one permanent magnet ring situatedabout the impeller and the housing, with polarities arranged so thatpositive radial stiffnesses are generated and soft magnetic iron isemployed on one or more of the ring faces to focus the magnetic fluxbetween the permanent magnet rings, such that the impeller operates in acentered position relative to the two radial displacements for controlof two of the six axes.
 17. The apparatus of claim 16, wherein a firstimpeller magnetic target set and the first housing electromagneticbearing set comprise electromagnetic bearings which control theremaining axial displacement and two angular displacements of the sixaxes so that the impeller operates in a centered position with regard tothese three axes, a third angular axis being controlled by the motor.18. The apparatus of claim 1, further comprising a positioning structurefor controlling six axes of impeller motion, said positioning structureincluding a hybrid magnetic bearing system wherein a first impellerpermanent magnetic bearing set and a first housing permanent magneticbearing set each comprise a set of multiple permanent magnet ringssituated about the impeller and the housing, with polarities arranged sothat positive radial stiffnesses are generated and soft magnetic iron isemployed on at least one of the ring faces to focus the magnetic fluxbetween the permanent magnet rings, such that the impeller operates in acentered position relative to the two radial displacements for controlof two of the six axes.
 19. The apparatus of claim 18, wherein a firstimpeller magnetic target set and the first housing electromagneticbearing set comprise electromagnetic bearings which control theremaining axial displacement and two angular displacements for controlof three of the six axes so that the impeller operates in a centeredposition with regard to these three axes.
 20. The apparatus of claim 1,further comprising a positioning structure for controlling six axes ofimpeller motion, said positioning structure including a hybrid magneticbearing system wherein a first impeller permanent magnetic bearing setand a first housing permanent magnetic bearing set each comprise a setof multiple permanent magnet rings situated about the impeller and thehousing, with polarities arranged so that positive radial stiffnessesand positive moment stiffness are generated and soft magnetic iron isemployed on at least one of the ring faces to focus the magnetic fluxbetween the permanent magnet rings, such that the impeller operates in acentered position relative to the two radial displacements and the twoangular displacements for control of four of the six axes.
 21. Theapparatus of claim 20, wherein a first impeller magnetic target set andthe first housing electromagnetic bearing set comprise electromagneticbearings which control the remaining axial displacement of the six axesso that the impeller operates in a centered position with regard to thisaxis.
 22. The apparatus of claim 1, further comprising a positioningstructure for controlling six axes of impeller motion, said positioningstructure including a hybrid magnetic bearing system wherein the firstimpeller permanent magnetic bearing set and the first housing permanentmagnetic set each comprise a set of multiple permanent magnet ringssituated about the impeller and the housing, with polarities arranged sothat positive axial stiffness and positive moment stiffnesses aregenerated and soft magnetic iron is employed on at least one of the ringfaces to focus the magnetic flux between the permanent magnet rings,such that the impeller operates in a centered position relative to theaxial displacement and the two angular displacements for control ofthree of the six axes.
 23. The apparatus of claim 22, wherein the firstimpeller magnetic target set and the electromagnetic bearings controltwo radial displacements so that the impeller operates in a centeredposition with regard to these two axes.
 24. The apparatus of claim 1,wherein the plurality of magnetic actuators form a magnetic systemcomprising: a first construct permanent magnet disposed on a first wallof the hollow interior of the construct, a second construct permanentmagnet disposed on a second wall, opposite the first wall, of the hollowinterior of the construct, a first impeller permanent magnet disposed onthe impeller distal to the axial center of the construct and juxtaposedwith the first construct permanent magnet, a second impeller permanentmagnet disposed on the impeller distal to the axial center of theconstruct and juxtaposed with the second construct permanent magnet, afirst construct permanent magnet set disposed on the first wall of thehollow interior of the construct, a second construct permanent magnetset disposed on the second wall of the hollow interior of the construct,a first impeller permanent magnet set disposed on the impeller proximateto the axial center of the construct and juxtaposed with the firstconstruct permanent magnet set, and a second impeller permanent magnetset disposed on the impeller proximate to the axial center of theconstruct and juxtaposed with the second construct permanent magnet set,wherein the arrangement provides radial stabilization and, due toangular positioning, provides a degree of translational stabilization ofthe impeller and the impeller is prevented from contacting the hollowinterior of the construct by magnetic fields.
 25. The apparatus of claim24, wherein the magnetic system further comprises self correctingpositioner for dynamically positioning the impeller during operationsuch that the impeller is constantly out of contact with the construct.26. Apparatus of claim 24, wherein the magnetic system furthercomprises, at least one coil disposed in the first wall of the constructhousing and at least another one coil disposed in the second wall of theconstruct housing, the at least one coil being juxtaposed between (i)the first construct permanent magnet and (ii) the first constructpermanent magnet set, and at least another one coil being juxtaposedbetween (i) the second construct permanent magnet and (ii) the secondconstruct permanent magnet set; at least one electromagnetic thrustbearing disposed in the construct housing about the at least one coiland the at least another one coil; and an electronic controller forcontrolling electric current in at least one coil and at least anotherone coil thereby causing changes in forces exerted by at least oneelectromagnetic thrust bearing.
 27. Apparatus of claim 26, furthercomprising a physiological controller for controlling a rate of rotationof the impeller so that the rate of rotation corresponds to thephysiological state of a person using the apparatus of the presentinvention, said physiological controller being coupled to the electroniccontroller, said electronic controller further including a monitor formonitoring change of electronic parameters selected from the groupconsisting of (i) bearing currents in the at least one electromagneticthrust bearing, (ii) bearing voltages in the at least oneelectromagnetic thrust bearing, (iii) motor currents, and (iv) motorvoltages.
 28. The apparatus of claim 1, further comprising ofphysiological controller for controlling the rate of rotation of theimpeller so that the rate of rotation corresponds to the physiologicalstate of a person using the apparatus of the present invention.
 29. Theapparatus of claim 28, wherein the electronic controller comprises amonitor for monitoring change of electronic parameter selected from thegroup consisting of (i) bearing currents in at least one electromagneticthrust bearing; (ii) bearing voltages in at least one electromagneticthrust bearing; (iii) motor currents; and (iv) motor voltages.
 30. Theapparatus of claim 1, wherein the motor comprises a stator integrallyformed within a wall of the hollow interior of the construct, the statorhaving windings fixed therein for receiving current from a motorcontroller.
 31. The apparatus of claim 1 wherein the motor comprises arotor having a circumference integrally formed as part of the impeller,the rotor having a plurality of permanent magnets disposed therein suchthat (i) poles of the plurality of permanent magnets alternate betweennorth and south and (ii) the plurality of permanent magnets are arrangedto form a circular pattern concentric with the circumference of therotor.
 32. The apparatus as defined in claim 1, further comprising aplurality of electromagnetic segments which are individually controlledto provide the six axes of control.
 33. The apparatus as defined inclaim 1, wherein the magnetic actuators provide six axes of control,including (i) one axial translational axis, (ii) two radialtranslational axes, and (iii) three rotational axes comprising two axescontrolled for moment and one axis controlled by motor rotation.
 34. Theapparatus of claim 1, wherein the impeller comprises straight blades.35. A continuous flow pump for pumping sensitive biological fluidscomprising: a construct having a first pump housing half and a secondpump housing half hermetically sealed to the first pump housing half toform the construct, the construct having a hollow interior and an axialcenter; a pump inlet vessel formed from the first pump housing half andhaving an inlet throughbore for passage of fluids therethrough and intothe hollow interior of the construct; a pump outlet vessel radiallylocated from the axial center of the construct and formed from the firstand second pump housing halves and having an outlet throughbore forpassage of fluids therethrough from the hollow interior of theconstruct; an impeller disposed within the hollow interior of theconstruct and out of contact therewith and having an impeller intakeopening, impeller chambers, and impeller vanes having a spiral curvaturefor forming the impeller chambers; a magnetic system comprising aplurality of electromagnetic actuators to provide six axes of control,including (i) one axial translational axis, (ii) two radialtranslational axes, and (iii) three rotational axes comprising two axescontrolled for moment and one axis controlled by motor rotation, whereinat least one of the five axes controlled for moment, axial translation,and radial translation is controlled by a set of permanent magnets inthe housing magnetized in an axis parallel to the axis of rotation ofthe impeller, said electromagnetic actuators being positioned forsuspending the impeller out of contact with the hollow interior of theconstruct and for selectively rotating the impeller to thereby controlfluid flowing through the continuous flow pump; and a motor forcontrolling rotational speed of the impeller.
 36. A method for pumpingsensitive biological fluids using a pump comprising the steps of:selecting a pump device having a magnetically suspended impeller withina housing of the pump having at least one permanent magnet disposedtherein, the impeller having arcuately shaped vanes for reducing impacton the sensitive fluids traveling through the pump; positioning theimpeller within the housing according to signals received from amagnetic system that are used to magnetically suspend the impeller;controlling a plurality of electromagnetic actuators to provide six axesof control, including one axial translational axis and one rotationalaxes; positioning the electromagnetic actuators such that at least oneof the axes control is controlled by a set of permanent magnets in thehousing magnetized in an axis parallel to the axis of rotation of theimpeller; and adjusting the impeller rotational speed and thus the rateof fluid flow according to signals received frog an input and an outputof the pump.
 37. The method of claim 36, wherein controlling a pluralityof electromagnetic actuators further comprises controlling (i) one axialtranslational axis, (ii) two radial translational axes, and (iii) threerotational axes comprising two axes controlled for moment and one axiscontrolled by motor rotation.
 38. Apparatus for pumping sensitivebiological fluids comprising: a construct having an exterior, a hollowinterior having walls therein, at least one housing permanent magnetdisposed therein, and an axial center; an inlet formed from theconstruct exterior for passage of fluids therethrough and into thehollow interior of the construct; an outlet formed from the constructexterior for passage of fluids therethrough from the hollow interior ofthe construct, the outlet radially located from the axial center of theconstruct; an impeller disposed within the hollow interior of theconstruct and out of contact therewith for controlling fluid flow intothe inlet, through the hollow interior of the construct, and out of theoutlet, the impeller having arcuate blades and arcuate passagewayswhereby fluid flow through the construct is gradually redirected fromthe inlet to the outlet; a magnetic system including at least oneimpeller permanent magnet juxtaposed to the housing permanent magnet forsuspending the impeller out of contact with the hollow interior of theconstruct; and a motor which selectively rotates the impeller to therebycontrol fluid flowing through the apparatus, said motor including statorwindings formed within the housing of the construct and arcuately shapedpermanent magnets with a soft iron core formed as part of the impeller,said permanent magnets and soft iron core arranged such that magneticflux is present on only one side of the rotor, interacting with statorwindings on the same side.
 39. Apparatus for pumping sensitivebiological fluids comprising: a construct having an exterior, a hollowinterior having walls therein, at least one housing permanent magnetdisposed therein, and an axial center; an inlet formed from theconstruct exterior for passage of fluids therethrough and into thehollow interior of the construct; an outlet formed from the constructexterior for passage of fluids therethrough from the hollow interior ofthe construct, the outlet radially located from the axial center of theconstruct; an impeller disposed within the hollow interior of theconstruct and out of contact therewith thereby permitting fluid flowinto the inlet, through the hollow interior of the construct, and out ofthe outlet, the impeller having arcuate blades and arcuate passagewayswhereby fluid flow through the construct is gradually redirected fromthe inlet to the outlet; a magnetic system including at least oneimpeller permanent magnet juxtaposed to the housing permanent magnet forsuspending the impeller out of contact with the hollow interior of theconstruct; and a motor for selectively rotating the impeller to therebycontrol fluid flowing through the apparatus; wherein the impeller isintegrated with a rotor being controlled by the motor thereby allowingthe motor to control rotation of the impeller, the integratedcombination of the impeller and the rotor forming interior sides of afirst return flow chamber and a second return flow chamber,respectively, for permitting fluid flow around the suspended impeller;wherein the interior side of the impeller forming the first return flowchamber includes a first member having a curvature corresponding to acurvature of walls of the hollow interior of the construct; and whereinthe first member includes a first impeller permanent magnet forinteraction with a first housing permanent magnet and a first impellerpermanent magnet set for interaction with a first housing permanentmagnet set, wherein (i) the first impeller permanent magnet isjuxtaposed with the first housing permanent magnet such that a pole ofthe first impeller permanent magnet repels a pole of the first housingpermanent magnet and (ii) the first impeller permanent magnet set isjuxtaposed with the first housing permanent magnet set such that polesof the first impeller permanent magnet set repel poles of the firsthousing permanent magnet set thereby preventing contact between thefirst member and the housing; and wherein the first impeller magneticset and the first housing magnetic set each comprise a multiple ringconfiguration about the impeller and the housing, respectively, themultiple ring configuration of each magnetic set comprising at least onefirst magnetic ring and at least one second magnetic ring disposed in anattractive orientation with the at least one first magnetic ring and thefirst impeller magnetic set disposed in reverse polarity with the firsthousing magnetic set.
 40. Apparatus for pumping sensitive biologicalfluids comprising: a construct having an exterior, a hollow interiorhaving walls therein, at least one housing permanent magnet disposedtherein, and an axial center; an inlet formed from the constructexterior for passage of fluids therethrough and into the hollow interiorof the construct; an outlet formed from the construct exterior forpassage of fluids therethrough from the hollow interior of theconstruct, the outlet radially located from the axial center of theconstruct; an impeller disposed within the hollow interior of theconstruct and out of contact therewith to control fluid flow into theinlet, through the hollow interior of the construct, and out of theoutlet, the impeller having arcuate blades and arcuate passagewayswhereby fluid flow through the construct is gradually redirected fromthe inlet to the outlet; a magnetic system including at least oneimpeller permanent magnet juxtaposed to the housing permanent magnet forsuspending the impeller out of contact with the hollow interior of theconstruct; and a motor permitting selective rotation of the impeller tothereby control fluid flowing through the apparatus; wherein theimpeller comprises an integrated combination of an impeller for fluidflow through the construct and a rotor being controlled by the motorthereby allowing the motor to control rotation of the impeller, theintegrated combination of the impeller and the rotor forming interiorsides of a first return flow chamber and a second return flow chamber,respectively, for permitting fluid flow around the suspended impeller;wherein the interior side of the rotor forming the second return flowchamber includes a second member having a curvature corresponding to acurvature of walls of the hollow interior of the construct, the secondmember being coupled to a first member by the arcuate blades of theimpeller wherein impeller chambers are formed from (i) the arcuateblades, (ii) the first member, and (iii) the second member, thus formingthe arcuate passageways for the gradual redirection of fluid from theinlet to the outlet; wherein the second member includes a secondimpeller permanent magnet for interaction with a second housingpermanent magnet and a second impeller permanent magnet set forinteraction with a second housing permanent magnet set, wherein (i) thesecond impeller permanent magnet is juxtaposed with the second housingpermanent magnet such that a pole of the second impeller permanentmagnet repels a pole of the second housing permanent magnet and (ii) thesecond impeller permanent magnet set is juxtaposed with the secondhousing permanent magnet set such that poles of the second impellerpermanent magnet set repel poles of the second housing permanent magnetset thereby preventing contact between the second member and thehousing; and wherein the second impeller permanent magnetic set and thesecond housing permanent magnetic set each comprise a double ringconfiguration about the impeller and the housing, respectively, thedouble ring configuration of each magnetic set comprising a firstmagnetic ring and a second magnetic ring disposed in an attractiveorientation with the first magnetic ring and the second impellermagnetic set disposed in reverse polarity with the second housingmagnetic set.
 41. Apparatus for pumping sensitive biological fluidscomprising: a construct having an exterior, a hollow interior havingwalls therein, at least one housing permanent magnet disposed therein,and an axial center; an inlet permitting passage of fluids through theconstruct and into the hollow interior of the construct; an outletpermitting passage of fluids through the construct from the hollowinterior of the construct, the outlet radially located from the axialcenter of the construct; an impeller disposed within the hollow interiorof the construct and out of contact therewith the impeller; a magneticsystem including at least one impeller permanent magnet juxtaposed tothe housing permanent magnet, which is magnetized in an axis parallel tothe axis of rotation of the impeller for suspending the impeller out ofcontact with the hollow interior of the construct; and a motor inrotational engagement with the impeller to thereby control fluid flowingthrough the apparatus.
 42. The apparatus of claim 41, wherein theimpeller includes arcuate blades and arcuate passageways whereby fluidflow through the construct as gradually redirected from the inlet to theoutlet.